Thesis (MScConsEcol(Conservation Ecology and Entomology)--Stellenbosch University, 2008. / The Succulent Karoo biodiversity hotspot is threatened by pressure caused by increasing human populations and its associated land use types. Land use is primarily focussed on agriculture, with livestock grazing as a dominant land use in the region. Cultivation is also practiced along the major perennial rivers, and in drier areas, where this largely depends on rainfall. Only about seven percent of the biome is formally protected, and this area substantially under-represents the biodiversity of the Succulent Karoo and does not incorporate key ecological processes and biodiversity drivers. Therefore, there is urgent need for outside reserve conservation initiatives, whose success depend on understanding the ecosystem function of the Succulent Karoo. This study aimed to determine the impacts of heavy grazing, light grazing and cultivation (in a 30-year old fallow field) on assemblages of ground-dwelling and flying invertebrates. Seasonal assemblage changes were also determined. Vegetation structure and composition were determined using the line-intercept method to determine if vegetation patterns explain patterns in invertebrate assemblages. Abandoned fields harbour the lowest number of plant species, and these together with the heavily grazed sizes are dominated by a high cover of Galenia africana (Aizoaceae). Lightly grazed sites have the highest structural complexity, with a high cover of succulents and non-succulent perennials. After the winter rains, annual plants occupy most of the bare ground in heavily grazed and previously cultivated sites. Seasonal changes in assemblages of ground-dwelling and flying invertebrates were determined by sampling during the four seasons at the same localities. Results of pitfall traps sampling for ground-dwelling invertebrates and coloured pan traps for flying invertebrates showed that overall species richness and diversity peaked in spring for flying invertebrates while peaks in richness for ground-dwelling invertebrates were in summer, with no difference in overall diversity. Overall abundance for ground-dwelling invertebrates was highest in summer and lowest in winter. Ground-dwelling invertebrate fauna was dominated by Formicidae and Araneae. Grazing and cultivation lead to skewed community composition of ground-dwelling invertebrates which favours disturbance tolerant and generalist species such as Anoplolepis steingroeveri (Forel).

Thesis (MSc(Conservation Ecology and Entomology)--University of Stellenbosch, 2006. / The stomachs of 286 crocodiles (17 cm to 166 cm snout to vent length) were lavaged over a two year period. Crocodylus niloticus has a similar ontogenetic shift in diet to that of other crocodilians. Yearlings predated primarily on aquatic insecta and arachnida, as crocodile size increased (juveniles) the diet became more diverse including crustacea, amphibia and fish. The largest size class (sub-adults) consumed primarily fish. Yearlings fed consistently throughout the year, however a higher proportion of empty stomachs occurred within the juvenile and sub-adult size classes during the winter months. A captive experiment with wild caught crocodiles (0.7 kg - 20 kg) indicated a decrease in satiation rate (maximum mass of food eaten as a percentage of crocodile body mass) from 11.3 % to 6.5 % with an increase in crocodile size. Wild yearlings consumed 0.48 % of their body mass in prey per day, and juveniles, 0.23 %. The wild food conversion rates of natural prey were low, 32 % and 40 % for yearlings and juveniles respectively. This was possibly due to a high percentage of indigestible (chitinous) invertebrate mass in the diet. The percentage of stomach stone mass to crocodile body mass increased with crocodile size. Seven species of nematodes were found within the stomachs, four of which represent new geographic records.

Thesis (MScConsEcol (Conservation Ecology and Entomology)--University of Stellenbosch, 2009. / Apiculture in the Western Cape is a well-developed industry based on honey production and pollination services to agriculture. Apart from Eucalyptus trees, fynbos vegetation serves well as bee forage to managed honeybee colonies outside the agricultural pollination season. Eucalyptus trees are cleared as invasive plant species while fynbos are rigorously protected as one of the 34 Biodiversity Hotspots identified worldwide. Thus, bee forage is in short supply and is most probably the only limitation to the number of honeybee colonies that beekeepers can feasibly maintain. The impact of a collection of commercially managed honeybee colonies on other floral resource-dependent species in the Cape Floristic Region is unknown. This is one of the first studies on the topic in South Africa and specifically in the Western Cape. Managed hives were introduced to near pristine fynbos habitat in De Hoop Nature Reserve and Marine Protected Area during July. The aim was to induce stronger competition for floral resources through greater resource exploitation by managed honeybee colonies and record the change in foraging behaviour for several insect guilds on specific plant species. The results suggest that eight hives per site proved insufficient to increase honeybee density above the natural density of honeybees. Honeybee abundance did not increase during the presence of the managed hives, while honeybee visitation frequency was significantly greater during the presence of the managed hives. Neither the abundance nor the visitation frequency of non-Apis bees and wasps differed significantly between treatments. Honeybees were the most abundant foragers on the three focal plant species during all three treatments and also made the most visits to flowers. Honeybee abundance and visitation frequency increased with distance from the managed hives. The significant increase in honeybee visitation frequency during hive presence, coupled with a significant decrease in the time honeybees spent per flower extracting nectar, were an indication of a lower standing crop of nectar during that treatment. Nevertheless, no competition for floral resources was obvious, as the number of honeybees did not increase the abundance and visitation frequency of all other insect guilds (except for a significant decrease in Muscidae, which could be ascribed to changes in weather conditions).

Thesis (MSc (Conservation Ecology and Entomology)--University of Stellenbosch, 2006. / The Restionaceae is a dominant family in the Fynbos Biome, an area in which fire plays a role as an important disturbance, yet little is known about their population dynamics. Two species of the Restionaceae (Thamnochortus insignis and T. erectus) are economically important as thatching reed and differ in their life-histories. This study aims to determine the effects of variation in life history (sprouter vs. non-sprouter) on the population structure and dynamics of T. erectus (“wyfies riet”, sprouter) and T. insignis (“mannetjies riet”), a non-sprouting species. A matrix-modelling approach based on field data collected by Ball (1995) is used to determine population growth rates, stable stage distributions and stage sensitivity and elasticity for the two species with no disturbance present. The sprouter (T. erectus) shows a positive population growth rate (λ >1) and greater persistence within all stages. The non-sprouting species (T. insignis) shows a negative population growth rate (λ <1) between disturbances as well as greater seed production, germination and growth between stages. Based on the population dynamics of these two species, further research was done to understand the effect of disturbance (harvesting and fire) on these species. A matrix modelling approach was used to determine which disturbance frequency maximises population output and success. Harvesting as well as fire results in a decline in T. insignis populations. A five year frequency for harvesting results in the greatest output of adult plants with the lowest effect on the population, and a fire frequency of 50 to 65 years is recommended. Testing indicates that the model underestimates the number of adults in the population and thus the model is conservative. T. erectus populations grow despite fire or harvesting; thus any reasonable harvesting (3-5 year frequency) and fire (10+ years between fire) regime would ensure population persistence. As data were limited it was not possible to test the results although T. erectus appears resilient to disturbance and therefore a predetermined regime is not as important as in T. insignis. Recommendations to farmers are made based on these results.

Thesis (MScAgric)--Stellenbosch University, 1931. / ENGLISH ABSTRACT: This thesis is presented in partial fulfilment of the requirements for the degree of MSc. Agric in Entomology. In this work an attempt has been made to gather all the available literature on the family Pentatomidae and to work out keys where possible for the genera and species recorded in South Africa . The keys for the species in either the University Collection or those of the South Africa Museum did not present much difficulty as I had access to the latter through the courtesy of Dr gill and the museum Entomologist, Dr. A. J. Hesse. I especially wish to thank Dr. Hesse for his kind assistance in connection with this work. Where I had to rely on the meagre descriptions of some entomologists it has in a few cases been impossible for me to include some of species in the keys, but I have, however, incorporated the original descriptions of the species in this work. The writer hopes, that, with the aid of the drawings and the general descriptions, the keys will be of value for the correct determination of the members of this family. The Literature available on the South African Pentatomidae is very comprehensive and scattered through various publications, some of which are hardly obtainable . This is the first attempt which has been made in this country to co-ordinate the literature on this subject and it will doubtlessly prove of value to those entomologists who have not the time or the opportunity of working through the voluminous records on this interesting group. The work has been done under the direction of Dr. T. J. Potgieter, Professor of Entomology at the Stellenbosch-Elsenberg College of Agriculture of the University of Stellenbosch and I am greatly indebted to him for advice and the kindly way in which he assisted me.

Thesis (MSc (Agric) (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Ambient temperature plays a key role in insect-physiology, -population dynamics and ultimately -geographic distribution. Here, I investigate the survival of codling moth, Cydia pomonella (Linnaues) (Lepidoptera: Tortricidae), which is a pest of economic importance in pome fruit production, to a wide range of temperature treatments. In this thesis, I first explore how temperature affects the survival and limits to activity of codling moth and secondly investigate if thermal acclimation can improve field performance of moths used in sterile insect technique control programmes under ecologically relevant conditions. First, I found that absolute temperature as well as the duration of temperature exposure significantly affects adult C. pomonella survival. Lethal temperatures, explored between -20 °C to -5 °C and 32 °C to 47 °C over a range of durations, showed that 50% of the adult C. pomonella population killed at -12 °C and at 44 °C after 2 hrs for each treatment. At high temperatures a pretreatment at 37 °C for 1 hr dramatically improved survival at 43 °C for 2 hrs from 20% to 90% (p<0.0001). Furthermore, high temperature pre-treatments (37 °C for 1 hr) significantly improved low temperature survival at -9 °C for 2 hrs. In sum, my results suggest pronounced plasticity of acute high temperature tolerance in adult C. pomonella, but limited acute low temperature responses. Secondly, low-temperature acclimated laboratory-reared moths were recaptured in significantly higher numbers (d.f. = 2, χ2 = 53.13 p<0.001), by sex pheromone traps, under cooler conditions in the wild relative to warm-acclimated or non-acclimated moths. However, these improvements in low temperature performance in cold-acclimated moths came at a cost to performance under warmer conditions in the wild. This novel study demonstrates the importance of thermal history on C. pomonella survival and clear costs and benefits of thermal acclimation on field and laboratory performance, and thus, the potential utility of thermal pre-treatments for improved efficacy in the sterile insect technique programme for C. pomonella control under cooler, springtime conditions. Finally, on a global scale, this study highlights that low and high temperatures could play a role in CM adult survival through direct mortality and thus, may influence, or have influenced in the pest, population dynamics. / AFRIKAANSE OPSOMMING: Temperatuur speel ‘n belangrike rol in die fisiologie, populasiedinamika en geografiese verspreiding van insekte. In hierdie tesis ondersoek ek die rol van ‘n wye reeks temperature op die oorlewing van kodlingmot Cydia pomonella (Linnaues) (Lepidoptera: Tortricidae), ‘n sagtevrug pes-spesie van ekonomiese belang. Ek ondersoek hoofsaaklik die effek van temperatuur op die fisiologie en fiksheid van kodlingmot, asook die mate waartoe termiese akklimasie (‘n mate van aanpassing) die veldgedrag van die steriele insek beheer-metode (SIT), d.m.v. kodlingot, in relevante omgewingstemperature kan verbeter. Ek het (i) gevind dat die temperatuur en duur van die temperatuur toediening ‘n betekenisvolle toename in volwasse C. pomonella oorlewing tot gevolg het. In die deel van die studie is temperature tussen -20 °C en -5 °C and tussen 32 °C en 47 °C ondersoek oor ‘n reeks van 0.5, 1, 2, 3 en 4 ure van duur. In kort lei -12 °C en 44 °C vir 2 uur onderskeidelik tot die uitsterf van 50% van die volwasse C. pomonella populasie. Indien die motte vooraf gehou is by 37 °C vir ongeveer 1 uur, is oorlewing by 43 °C vir 2 ure betekenisvol verbeter van 20% tot 90% (p<0.0001). Hoër temperatuur vooraf-blootstellings (akklimasie), by 37 °C vir 1 uur, het daartoe gelei dat lae temperatuur lae-temperatuur-oorlewings by -9 °C vir 2 ure betekenisvol verbeter het. Oor die algemeen het die resultate gedui dat hoër akute temperatuurstoleransie in C. pomonella bestaan, maar beperkte akute lae-temperatuur reaksies bestaan. Verder het lae-temperatuur akklimasie (laboratorium geteelde) motte ‘n betekenisvolle hoër getal hervangste deur geslagsferomone in koeler omgewings opgelewer (v.i. = 2, χ2 = 53.13, p<0.001) in vergelyking met warmer-temperatuur geakklimatiseerder motte. Hierdie verbeteringe in laetemperatuur reaksies vanaf lea-temperatuur akklimasie groepe is teen ‘n koste teen warmer reaksie-toestande in die natuur geïs. Hierdie eersdaagse studie demonstreer die belang van historiese temperatuur op die oorlewing van C. pomonella. Die kostes- en voordele van termiese akklimasie op veld- en laboratoriumpopulasie reaksies en die potensiële gebruik daarvan in die verbetering van steriele insek tegniek programme, onder koeler omstandighede, is uitgelig. Laastens, beklemtoon hierdie studie die belangrikheid van temperatuur as bepalende faktor van kodlingmot-oorlewing en die invloed daarvan op die vrugte-pes populasiedinamika.

Thesis (MScConsEcol)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Decision-making in conservation should be efficient and effective as time and resources are typically limited. Conservation planning is one process by which stakeholders collaboratively make decisions when attempting to ensure the persistence of biodiversity. Spatial prioritization is the activity of applying quantitative data to spatial analysis to select locations for conservation investment and is a distinct process within conservation planning. The use of experts in spatial prioritization, and more generally in conservation planning, is widely accepted and advocated, but there is no general operational model for how best to involve them. Acceptable standards of practice in selecting experts and in applying specific techniques for eliciting expert knowledge need to be developed and tested in different contexts to ensure robust and defensible results of spatial prioritization processes. Although experts and expert knowledge have limitations, including them in spatial prioritization can produce many benefits, such as increased robustness of decisions and time and cost savings. Timeous, decisive, cost-efficient and robust decision-making is essential when attempting to stem the continued loss of biodiversity across the world. Although widely used, very little research has been conducted into the role of experts in spatial prioritization processes. In this research, the role and use of experts and expert knowledge in spatial prioritization was explored through the following processes: 1) a review of the peer-reviewed literature examining the role, and different types, of experts included in spatial prioritization studies (Chapter 2) to identify the patterns of their involvement; 2) a study examining the process and the differences between individual and group expert outputs and outcomes produced from a typical spatial prioritization workshop to provide a baseline against which experts might be identified for future involvement (Chapter 3); and 3) a study examining the knowledge of local community and land management experts and their ability to predict private landowners self-reported attitudes towards conservation, willingness to partner with organizations and behavior relating to conservation, aimed to test if expert knowledge might replace interviews when mapping conservation opportunity (Chapter 4). The main findings of this research are, firstly, that experts primarily contributed to spatial prioritization through mapping of species, habitats and ecosystems (that can be input into spatial prioritization analyses), and specifically also the selection of areas important for implementing conservation action (e.g., priority conservation areas). Secondly, individual experts contributed different expertise to the spatial prioritization processes in which they were involved, sometimes despite being considered experts in the same field. Individual experts differed to each other in the knowledge they contributed, decisions they made, and in the information content and its spatial representation. Groups of experts collaborating to produce the same information were more effective at capturing expert knowledge than individuals. Thirdly, when seeking to map human and social data to inform the mapping of conservation opportunity, experts were unable to reliably score private landowner's attitudes towards conservation, willingness to partner with organizations and behavior relating to conservation. Experts were able though, to provide accurate knowledge on the general attitudes of landowners, the context of the area in which the research was conducted, and the challenges that landowners in the area face. Collectively, this research can be used to inform the development of standards of best practice to ensure the most effective and cost efficient approach to integrating spatial prioritization software with expert knowledge. / AFRIKAANSE OPSOMMING: Besluitneming in bewaring moet doeltreffend en effektief wees omdat tyd en hulpbronne skaars is. Bewaringsbeplanning is een proses waardeur aandeelhouers gesamentlik besluite kan neem wanneer hul poog om die voortbestaan van biodiversiteit te verseker. Ruimtelike prioritisering verwys na die proses waar kwantitatiewe data toegepas word op ruimtelike analise om areas vir bewaringsbelegging te selekteer. Dit is 'n afsonderlike proses binne bewaringsbeplanning. Die gebruik van deskundiges in die bepaling van ruimtelike prioritisering en meer algemene bewaringsbeplanning word wyd aanvaar en bepleit maar daar is geen algemene operationele model wat bepaal hoe om hul ten beste in te sluit nie. Aanvaarbare standaarde in die praktyk van die seleksie van kundiges en die aanwending van spesifieke tegnieke om kundige kennisstelsels uit te lok moet ontwikkel en getoets word in verskillende kontekste om robuuste en verdedigbare resultate te verseker. Daar is baie voordele verbonde aan die gebruik van deskundiges en kundige kennisstelsels, ten spyte van hul beperkings. Voordele sluit onder andere tyd- en kostebesparings in. Tydige, beslissende, koste-effektiewe en robuuste besluitneming is noodsaaklik wanneer daar gepoog word om die voortdurende wêreldwye verlies aan biodiversiteit te stuit. Al word hul algemeen gebruik is daar nog baie min navorsing gedoen oor die rol van kundiges tydens die proses van ruimtelike prioritisering. Die rol en gebruik van kundiges en kundige kennisstelsels in die bepaling van ruimtelike prioritisering is deur die volgende prosesse ondersoek: 1) 'n Oorsig van portuurbeoordeelde literatuur wat die rol van en verskillende tipes kuniges wat in ruimtelike prioritisering studies ingesluit word, bestudeer (Hoofstuk 2) ten einde die patrone van hul betrokkenheid te identifiseer; 2) 'n studie wat die proses en verskille tussen die insette en uitkomste van individuele en groepe kundiges, soos geproduseer by 'n tipiese ruimtelike prioritisering werkwinkel, bestudeer ten einde 'n grondlyn daar te stel waarteen kundiges vir toekomstige betrokkenheid geïdentifiseer kan word (Hoostuk 3); en 3) 'n bestudering van die kennis van plaaslike gemeenskaps- en grondbestuur kundiges en hul vermoë om privaat grondeienaars se selfgerapporteerde houdings teenoor bewaring, hul bereidwilligheid om met organisasies saam te werk en gedrag wat verband hou met bewaring te voorspel om te toets of kundige kennis onderhoude sal kan vervang tydens die kartering van bewaringsmoontlikhede (Hoofstuk 4). Die vernaamste bevindinge van hierdie navorsing is, ten eerste, dat kundiges se primêre bydrae tot ruimtelike prioritisering plaasvind deur die kartering van spesies, habitats en ekosisteme (wat alles in ruimtelike prioritisering analise vervat kan word), en meer bepaald die seleksie van areas wat belangrik is vir die implementering van bewaringsaksie (bv. prioriteit bewaringsareas). Tweedens, individuele kundiges se bydrae tot die ruimtelike prioritisering prosesse waar hul betrokke was, het verskil, selfs waar hul as kundiges in dieselfde veld beskou word. Individuele kundiges het van mekaar verskil ten opsigte van die kennis wat hul bygedra het, die besluite wat hul geneem het, die inhoud van inligting en die ruimtelike voorstelling daarvan. Groepe kundiges wat saamwerk om dieselfde inligting op te lewer was meer effektief in die vaslegging van kundige kennis as individuele kundiges. Derdens, tydens die soeke na menslike en maatskaplike data om die kartering van bewaringsmoontlikhede in te lig was kundiges nie in staat is om 'n betroubare skatting van privaat grondeienaars se houdings teenoor bewaring, bereidwilligheid om saam met organisasies te werk en gedrag wat verband hou met bewaring te maak nie. Deskundiges kon egter akkurate kennis meedeel ten opsigte van die algemene houdings van grondeienaars, die konteks van die area van navorsing en die uitdagings wat grondeienaars in die spesifieke areas in die gesig staar. Hierdie navorsing kan gesamentlik gebruik word om die ontwikkeling van standaarde van beste praktyk vas te stel om die mees doeltreffende en koste-effektiewe benadering tot die integrasie van ruimtelike prioritisering sagteware met deskundige kennis te verseker.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Plant-parasitic nematodes, consisting of a wide range of species, can cause severe economic losses in most agricultural food crops. Meloidogyne spp. (root-knot nematodes), Criconemoides xenoplax (ring nematode), Xiphinema index (dagger nematode) and Pratylenchus spp. (lesion nematodes) are some of the economically important plant-parasitic nematodes that pose a threat to viticulture and other perennial crops in South Africa. Worldwide there is ever-increasing pressure on pre-plant synthetic soil fumigants and post-plant nematicides. For sustainable nematode management, it is important to have a holistic approach; taking into consideration cultural, biological and chemical options as part of an integrated management approach. Biofumigation has the potential to fit into such an integrated management system and previous research indicates the positive response on soil-borne diseases, nematodes and weeds. Biofumigation occurs where certain plant species, containing glucosinolates (GSL) in the vacuole of the plant cells, come into contact (after cell maceration), with the enzyme myrosinase (MYR) situated in the cytoplasm of the cell, to form active compounds such as isothiocyanate (ITC). When this green manure is applied to infested soil, the ITC has the potential to have a direct suppressive effect on the soil-borne pathogens and there is also an indirect effect that can be expected after green manure soil amendment, because microbial activity is enhanced in the soil. Brassicas are known to possess GSL and MYR in their cells and thus have the potential to be utilized as biofumigation crops. There are, however, differences in the potential within the Brassicaceae family, based on different types and concentrations of GSL present in the different species. To ensure effective biofumigation it is important to use the correct brassica species and have a good understanding of the factors that have a positive impact on the biofumigation action. Laboratory bioassays were done to determine the potential of different cover crops to suppress Meloidogyne javanica and C. xenoplax, when applied as a green manure. The cover crops used for the bioassays included Oats (Avena sativa cv. Pallinup), White mustard (Sinapis alba cv. Braco), Canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199) and Nemat (Eruca sativa cv. Nemat). The plant material was cut into small pieces and mixed with sterilised soil inoculated with either M. javanica or C. xenoplax. Results from the bioassays showed a significant suppression of M. javanica by the three biofumigation species: White mustard, Caliente 199 and Nemat. These results supported previous research, indicating the nematode suppressing effect due to the biofumigation action of certain brassica crops. Canola did not have the same suppressing impact on the M. javanica and gave comparable results to the control, indicating that Canola is not a good biofumigation crop for M. javanica suppression. In terms of biofumigation effect oats did not differ significantly from the control or the three brassicas: White mustard, Caliente 199 and Nemat. In the bioassays done for C. xenoplax no significant differences were found between the green manure treatments and the control. These results indicate that the different crops tested, including the three well known biofumigation crops, did not suppress the C. xenoplax at the applied biomass concentrations used in the bioassay. Crops can also be classified according to their host status for certain plant parasitic nematodes. Crop host trials were conducted to determine the crop host status of the five different cover crops, to M. javanica and C. xenoplax. The crops were planted in sterilised soil, inoculated with the latter plant-parasitic nematodes and left for 60 days, after which, a root gall index analysis was done for M. javanica and for 85 or 92 days after which C. xenoplax was extracted from the soil. All the crops evaluated had a significantly lower root gall index for M. javanica than the control. Nemat and Oats was classified as poor hosts for M. javanica. A visual inspection of the root systems of all the crops was performed to determine whether M. javanica managed to complete its lifecycle in the different root systems. On all root systems, M. javanica managed to form root galls and produce egg masses, from which (J2) juveniles emerged. This indicates that M. javanica did complete its lifecycle in the different root systems of the crops evaluated and that all the cover crops acted as hosts. The expression of the gall symptoms were, however, less severe on Nemat and Oats, compared to the others. In the C. xenoplax crop host trials, all except the Nemat treatment showed a significant difference, compared to the Tomato treatment, with lower C. xenoplax numbers being present in the other crops. The nematode numbers in the different crops, compared well with the control (only inoculated soil), indicating that the crops did not stimulate the reproduction of C. xenoplax. Canola had the lowest numbers of C. xenoplax present after the growing cycle and Caliente 199 also showed a declining trend. In South Africa, the use of annual cover crops in vineyards is an established soil cultivation practice. In a field study, Oats, White mustard, Canola, Caliente 199 and Nemat were established in a vineyard as cover crops for three growing seasons (2009/10, 2010/11, 2011/12), and evaluated for their biofumigation impact, as well as their host impact on the suppression of certain economically important plant-parasitic nematodes. Two cover crop management practices, namely mechanical incorporation (MC) into the top soil and chemical removal of the cover crop (CC) were applied to the different cover crops. Nematode samples were taken in the work row and in the vine row at different times to determine the nematode status. These periods were April/May, before planting the cover crops, as well as 0, 15, 30 and 60 days after the management practices were performed. The crop biomass, measured as dry matter production (DMP) in tons/ha, differed significantly between the different crops, but also showed substantial increases during the three cover crop growing seasons for most crops. During the three consecutive seasons, Canola (CC) and Caliente 199 (CC) showed a constant reduction in the C. xenoplax population in the vine row based on the 60 day analysis. This trend was also observed for the total plant-parasitic nematode population in the vine row for the three seasons, based on 60 day analysis. The same trend took place during the three-year trial period for all the different sampling periods (0, 15, 30 and 60 days). The results can be attributed to the host status of these crops and not primarily because of the biofumigation effect. Both the Canola (CC) and the Caliente (CC) had a substantial increase in DMP during the three growing seasons that might have played a role in this trend. White mustard (CC and MC) showed a significant increase in the C. xenoplax population in the vine row, over the three year period, based on the 60 day analysis. The same trend was found Nemat (CC) and weeds and nematicide (CC) measured at the same period. A positive result from the Meloidogyne sp. analysis was that there was no significant increase in the Meloidogyne sp. in the vine row during the three growing seasons based on the 60 day analysis. This trend was seen in all the different treatments. The results from this study opens the possibility to apply these cover crops as part of a crop rotation programme without expecting an increase in the Meloidogyne sp. population to occur in the vine row through time. / AFRIKAANSE OPSOMMING: Plantparasitiese nematodes, wat bestaan uit 'n wye verskeidenheid van spesies, kan lei tot ernstige ekonomiese verliese in die meeste landbou gewasse. Meloidogyne spp. (knopwortel nematode), Criconemoides xenoplax (ring nematode), Xiphinema index (dolk nematode) en Pratylenchus spp. (letsel nematode) is van dié belangrikste plantparasitiese nematodes wat 'n bedreiging inhou vir wingerd en ander meerjarige gewasse in Suid-Afrika. Wêreldwyd is daar tans toenemende druk op die uitfasering van voor-plant chemiese grondberoking middels en so ook op nauitplant nematisiede. Vir volhoubare nematode bestuur, is dit belangrik om 'n holistiese benadering te volg, in ag genome kulturele, biologiese en chemiese maatreëls as deel van 'n geïntegreerde benadering. Bioberoking het die potensiaal om deel uit te maak van so 'n geïntegreerde benadering en baie vorige navorsing bevestig hierdie positiewe reaksie, in terme van onderdrukking, wat bioberoking op grond-gedraagde siektes, nematodes en onkruid kan hê. Bioberoking kan beskryf word as die reaksie, wat plaasvind wanneer glukosinolaat (GSL), wat teenwoordig is in die vakuool van die plantselle, in kontak kom met die ensiem mirosinase (MYR), nadat selbreking plaasgevind het en die aktiewe verbinding isothiosianaat (ITC) en ander sekondêre metaboliete gevorm word. Wanneer hierdie groen plantmateriaal in die grond ingewerk word, kan ʼn direkte onderdrukkings effek, as gevolg van die ITC, asook ʼn indirekte onderdrukkings effek as gevolg van die stimulasie van mikrobe aktiwiteit, verwag word. Brassica gewasse is bekend daarvoor dat daar GSL en MYR in die plantselle teenwoordig is en hulle besit dus die potensiaal om ITC te vorm. Daar is egter verskille in hierdie potensiaal binne die Brassicaceae familie, wat gebaseer is op verskillende tipes en konsentrasies GSL. Die keuse van ʼn brassica spesie is dus belangrik, tesame met ʼn verskeidenheid van ander faktore, om optimale bioberoking te verseker. Laboratorium biotoetse is gedoen om die bioberokings effek van verskillende dekgewasse op Meloidogyne javanica en C. xenoplax, wanneer dit aangewend word as groenbemesting, te bevestig. Die dekgewasse wat gebruik is sluit in: Hawer (Avena sativa cv. Pallinup), Wit mosterd (Sinapis alba cv. Braco), Canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199) en Nemat (Eruca sativa cv. Nemat). Die plantmateriaal is fyn opgesny en ingewerk in gesteriliseerde grond wat met onderskeidelik M. javanica en C. xenoplax geïnokuleer is. Resultate van die biotoetse vir M. javanica toon dat die drie gewasse; Wit mosterd, Caliente 199 en Nemat, wat alombekend is vir hul bioberoking potensiaal, ʼn betekenisvolle onderdrukkings op M. javanica tot gevolg gehad het. Hierdie biotoetse ondersteun vorige navorsing, waar effektiewe onderdrukking van sekere Meloidogyne spesies as gevolg van bioberoking verkry is. Die resultate dui ook aan dat Canola nie ʼn goeie opsie is vir effektiewe bioberoking om M. javanica onderdrukking te verkry nie. Die Hawer behandeling het nie betekenisvol van die kontrole of van die ander bioberokings gewasse verskil nie. Daar is geen betekenisvolle verskille verkry tussen die kontrole en die ander gewasse tydens die C. xenoplax biotoetse nie. Die resultate dui aan dat die dekgewasse, insluitende die drie bekende bioberokings gewasse, nie C. xenoplax onderdruk teen die toegediende biomassa konsentrasies nie. Gewasse kan ook geklassifiseer word op grond van hul gasheer status vir sekere nematode. Gasheer toetse is gedoen om die gasheer status van die verskillende dekgewasse vir M. javanica en C. xenoplax te bepaal. Dieselfde vyf verskillende dekgewasse is geplant in grond, wat vooraf onderskeidelik met M. javanica en C. xenoplax geïnokuleer is. Plante is gelos om vir `n spesifieke periode te groei waarna ʼn galindeks evaluasie is gedoen om die gasheer status vir M. javanica te bepaal en ʼn nematode ontleding gedoen is om die gasheer status vir C. xenoplax te bepaal. In die M. javanica gasheer toetse was die galindeks van al die gewasse betekenisvol laer as die kontrole. Nemat kan geklassifiseer word as ʼn swak gasheer vir M. javanica en het betekenisvol minder galle as al die ander gewasse, behalwe die Hawer, waarvan dit nie betekenisvol verskil het nie. Nemat pas dus goed in ʼn dekgewas program waar die doel is om die M. javanica populasie te onderdruk tydens die groei van die gewas. ʼn Visuele inspeksie van die wortelstelsels is ook gedoen ten einde te bepaal of die lewensiklus van M. javanica voltooi is. Wortelgalle en eiersakkies was teenwoordig in die wortels van al die verskillende gewasse en larwes het uit die eiers uitgebroei. Dit dui aan dat M. javanica daarin geslaag het om sy lewenssiklus op al die dekgewasse suksesvol te voltooi. Daar was aansienlik minder eiersakke by Nemat en Hawer; wat hul swak gasheer status bevestig. In die biotoetse vir die gasheerstatus van C. xenoplax het al die gewasse, behalwe Nemat, betekenisvol laer C. xenoplax getalle, in vergelyking met die Tamatie behandeling, tot gevolg gehad. Die nematode getalle was soortgelyk aan die kontrole (slegs geïnokuleerde grond), waar geen gewas in medium geplant is nie, en dui dus aan dat die getalle op die verskillende gewasse nie vermeerder het nie. Die Canola behandeling het die laagste C. xenoplax getalle gehad, gevolg deur Caliente 199. Hierdie gewasse toon dus die meeste potensiaal om aangewend te word in 'n rotasie stelsel of dekgewas program, waar die doel is om die C. xenoplax populasie te onderdruk. In Suid-Afrika is die aanwending van spesifieke eenjarige gewasse, as dekgewasse in wingerde, reeds ʼn standaard praktyk met verskeie voordele. In veldproewe oor ʼn tydperk van drie jaar (2009/10, 2010/11, 2011/12) is Hawer, Wit mosterd, Canola, Caliente 199 en Nemat aangeplant as dekgewasse in ʼn wingerd proefperseel. Die doel van die veldproewe was om die effek van dekgewasse op die plantparasitiese nematodes, wanneer dit aangewend word as bioberokings gewasse, te bepaal. Die gasheer status van die gewasse is ook ondersoek om te bepaal wat die effek sal wees op die nematode getalle. Twee dekgewas bestuurspraktyke is toegepas; meganiese inwerk van die dekgewasse in die bogrond (MC) en chemiese beheer van die dekgewasse (CC) en nematode monsters is op verskillende tye in die werksry en in die wingerdry geneem. Hierdie periodes sluit in April/Mei, voor die vestiging van die dekgewasse en 0, 15, 30 en 60 dae nadat die bestuurspraktyk toegepas is. Die dekgewas se biomassa produksie is, op grond van die droë massa produksie (DMP), in ton/ha gemeet, wat betekenisvol verskil het vir die verskillende dekgewas. Daar het ook `n duidelike toename in DMP plaasgevind oor die drie seisoene vir meeste gewasse. Gedurende die drie jaar periode het die Canola (CC) en Caliente 199 behandelings, gemeet 60 dae na die bestuurspraktyk, ʼn konstante afname getoon in die C. xenoplax in die wingerd ry. Dieselfde tendens het ook voorgekom gedurende hierdie periode in die totale plantparasitiese nematodes teenwoordig in die wingerd ry. Daar is ook ʼn geleidelike afnemende tendens in die C. xenoplax in die wingerd ry, oor die verskillende periodes 0, 15, 30 en 60 dae vir die drie opeenvolgende seisoene, waargeneem. Hierdie resultate kan primêr toegeskryf word aan die gasheer status van die dekgewasse, wat in die gasheer proewe as swak gashere vir C. xenoplax aangetoon is. Nog ʼn faktor wat hier ʼn rol speel is die feit dat beide die Canola (CC) en die Caliente 199 (CC) ʼn toename in DMP van meer as 2 ton, gedurende die drie jaar periode, gehad het; wat op sigself ook ʼn bydraende rol kon speel. Wit mosterd (CC en MC) het oor die drie seisoene ʼn betekenisvolle verhoging in die C. xenoplax populasie tot gevolg gehad, gebaseer op die 60 dae ontleding. Dieselfde tendens is ook opgemerk vir die ander behandelings, onder andere Nemat (CC) en die onkruid en aalwurmdoder (CC) behandeling. ʼn Baie positiewe resultaat na afloop van die drie seisoene is die feit dat daar nie ʼn betekenisvolle verhoging in die Meloidogyne sp. populasie in die wingerdry, op grond van die 60 dae onledings, plaasgevind het nie. Dit was ook die geval vir al die ander behandelings. Hierdie resultate ondersteun die moontlikheid om hierdie bioberokings gewasse deel te maak van ʼn geïntegreerde dekgewas benadering, sonder om in die proses die Meloidogyne sp. in die wingerd ry te verhoog.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The export of South African fruit to some of its biggest international markets may be rejected if the phytosanitary pest, Phlyctinus callosus (Coleoptera: Curculionidae) is found in fruit consignments. An alternative to methyl bromide fumigation is needed and one of the most promising of the alternative treatments is phytosanitary irradiation as it is environmentally friendly, does not leave residues on food or in the environment and it is effective against a wide variety of insects. Field-collected weevils were treated with five doses of gamma irradiation (5, 10, 20, 40 and 80 Gy) and the fecundity and fertility of mating crosses of treated males and females with treated and untreated individuals of the opposite sex, were determined to evaluate the effect on P. callosus reproductive ability post-treatment. Results indicated that irradiation treatment did not affect fecundity, but fertility was significantly affected, decreasing as the irradiation dose increased. Females were more susceptible to the irradiation treatment than males, and after treatment with 80 Gy, eggs laid by females and mated with either treated or untreated males, did not hatch. A generic dose of 400 Gy for all insect pests except tephritid fruit flies and pupae and adult Lepidoptera is currently approved by USDA-APHIS (United States Department of Agriculture – Animal and Plant Health Inspection Services) for use on certain commodities. Results from the present study support the development of a species-specific dose for P. callosus, as well as the development of a group generic dose for the Curculionidae that is lower than 400 Gy. Effective phytosanitary irradiation treatments are only feasible if the treatment does not adversely affect fruit quality and the marketability of export fruit. Therefore, an investigation of the effects of irradiation disinfestations treatments on the quality of the new pluot cultivar, ‘Flavor Fall’ was made. Packed cartons were treated with three doses of gamma irradiation: 400 Gy, 900 Gy and 1400 Gy. After treatment fruit underwent a PD 7 dual temperature cold storage regime for 42 days and a shelf-life simulation for 7 days. The impact of insect-proof bags, sometimes required by importing countries to keep insects off packaged fruit, was also investigated. Respiration rate of the fruit was measured throughout and fruit quality evaluations were done after cold storage and after shelf-life. The results indicated that quality parameters measured at the end of cold storage, which would be after the fruit arrives at the export markets, were above the minimum standards for overseas markets. Gel breakdown was unacceptably high after the higher temperature exposure of shelf-life for fruit treated with the 900 and 1400 Gy doses. The insect-proof bags reduced shrivel, but resulted in higher incidence of gel breakdown. The use of irradiation, together with the use of the insect-proof bag, has potential as an alternative postharvest mitigation treatment for plums. Lastly, an investigation into potential rearing methods for P. callosus, including recommendation for the future, was made as the availability of a sustainable rearing method that ensures a consistent supply of high quality P. callosus adults would enable continuous research with greater numbers of this pest. The information generated in this study provides a greater understanding of the radiation biology of, not only this curculionid species, but the Curculionidae as a group, and is valuable in advancing the development of alternative postharvest control measures against this phytosanitary pest. / AFRIKAANSE OPSOMMING: Suid Afrikaanse vrugte uitvoere na van die grootste internasionale markte mag weg gewys word as die fitosanitêre pes, Phlyctinus callosus (Coleoptera: Curculionidae) in die versending gevind word. ‘n Alternatief vir metiel bromied beroking word benodig en een van die mees belowende alternatiewe behandelings is fitosanitêre bestraling aangesien dit omgewings vriendelik is, nie residue op kos of in die omgewing los nie, en effektief is teen ‘n wye verskeidenheid van insekte. Veldversamelde kalanders is behandel met vyf dosisse gamma bestraling (5, 10, 20, 40 en 80 Gy) waarna die vrugbaarheid van paringskruisings bepaal is deur kruisings tussen behandelde manlike en vroulike kalanders met behandelde en nie-behandelde individue van die teenoorgestelde geslag te maak, en so die na-behandelings effek op die voortplantings vermoeë van P. callosus te evalueer. Die resultate het getoon dat die bestralings behandeling geen invloed gehad het op die hoeveelheid eiers wat gelê is nie, maar dat die uitbroei van eiers aanduidend geaffekteer is deur die behandeling. Die hoeveelheid eiers wat uitgebroei het, het minder geraak soos die bestralings behandeling toegeneem het. Vroulike kalanders was meer sensitief vir die behandeling en na 80 Gy, of hul gekruis is met behandelde of niebehandelde mannetjies, het geen eiers uitgebroei nie. ‘n Generiese dosis van 400 Gy vir alle insekte, uitsluitend tephritiese vrugte vlieë en papies en volwasse Lepidoptera is huidiglik goedgekeur deur die USDA-APHIS (United States Department of Agriculture – Animal and Plant Health Inspection Services) vir sekere kommoditeite. Die resultate van die huidige studie ondersteun die ontwikkeling van ‘n spesie-spesifieke dosis vir P. callosus, so ook die ontwikkeling van ‘n generiese groep dosis vir Curculionidae wat laer as 400 Gy is. Effektiewe fitosanitêre bestralings behandeling is slegs moontlik indien die behandelings dosis nie nadelig vir vrugkwaliteit en die bemarking van uitvoer vrugte is nie. Dus is die effek wat bestralings bestryding behandeling op die kwaliteit van ‘n nuwe pluot kultivar, ‘Flavor Fall’ ondersoek. Vrugte verpak in kartonne is met drie dosisse gamma bestraling behandel: 400 Gy, 900 Gy en 1400 Gy. Na behandeling is die vrugte deur ‘n PD 7 dubbel temperatuur koelopbergings regime van 42 dae en rak-lewe simulasie vir 7 dae gesit. Die impak van insek-bestande sakke wat insekte van die verpakte vrugte weg hou en soms deur invoerende lande ‘n vereiste is, is ook ondersoek. Respirasie tempo van die vrugte is getoets en vrugkwaliteit evaluasies is gedoen na koelopberging en rak-lewe. Die resultate het getoon dat die kwaliteits maatstawwe wat getoets is na koelopberging (wat tipies is wanneer die vrugte by die uitvoer mark arriveer), almal bo die minimum standaarde van die uitvoer markte was. Gel-afbraak was onaanvaarbaar hoog na blootstelling aan die hoër temperature tydens rak-lewe vir vrugte wat behandel is met 900 en 1400 Gy. Die insek-bestande sakke het verrimpeling verminder, maar die voorkoms van gel-afbraak vermeerder. Die gebruik van bestraling, tesame met die insek-bestande sakke, het potensiaal as alternatiewe na-oes behandeling vir pruime. Laastens is ‘n ondersoek ingestel vir moontlike teeltegnieke vir P. callosus en aanbevelings gemaak vir toekomstike studies. Die beskikbaarheid van ‘n volhoubare teeltegniek wat konstante, hoë kwaliteit P. colossus individue verskaf sal aaneenlopende navorsing met groter getalle van die pes moontlik maak. Die inligting wat deur hierdie studie gegenereer is help om die bestralings biologie, nie net van hierdie curculionid spesie nie, maar die Curculionidae as ‘n groep te verstaan, en is kosbaar in die bevordering van ontwikkeling van alternatiewe na-oes beheer meganismes teen hierdie fitosanitêre pes.

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH SUMMARY: Climate change and biological invasions are major components of global change induced by human activity and are considered major drivers of global biodiversity decline in terrestrial ecosystems. These drivers interact synergistically and render ecosystems vulnerable to invasion by invasive alien species. Grasses are a group of invasive plants that easily respond to global changes and alter native plant community structure and ecosystem processes, such as fire frequency. To date there have been few studies that assess the ecological drivers and effects of invasive grass species on arid and semi-arid ecosystems of South Africa. Fountain grass (Pennisetum setaceum) is a widely distributed invasive alien perennial grass from North Africa and the Middle East, valued by horticulturalists worldwide. It spreads along the edges of roads on the outskirts of most towns, and is common on mine spoil in many areas throughout South Africa. Occasionally, it escapes into natural vegetation along drainage lines or after fires. This grass can be a costly problem for agriculture and biodiversity conservation as it is unpalatable and increases fire risk. Understanding its distribution and invasive dynamics will contribute to better management and control practices. The main objective of this study was to understand the ecology and invasion processes of P. setaceum across South African environmental gradients, and use it as a model to understand the synergistic relationships between biological invasions and other global change (climate and land use) scenarios. This study provides the first assessment of how P. setaceum overcomes different invasion barriers in South Africa as an emerging invader, in comparison with other parts of the world where it has already become problematic. A number of management and control options for this grass and other similar perennial grasses result from this study. Specifically, the study provides comprehensive understanding of: 1) the distribution and habitat preferences of P. setaceum in arid and semi-arid parts of South Africa, 2) environmental resources and habitat conditions that promote its invasive potential, 3) growth and reproductive performance across environmental gradients, 5) the response of an arid ecosystem to P. setaceum invasion and fire promotion, and 6) the predicted future distribution of this grass in South Africa under scenarios of climate change and spread. The study has found that road-river interchanges are ideal sites for P. setaceum growth and that these sites should be targeted for management and control of this species. P. setaceum was found to persist under diverse biome environments, which is attributed to local adaptation. Disturbance was found to be a major factor promoting fountain grass invasion into semi-natural areas away from roadsides. Major clean-ups of this grass should focus on disturbed areas, especially in the fertile parts of the fynbos region where the grass has high climatic suitability. Management and control should also focus on areas with high nutrients and extra water, as these areas facilitate growth and reproduction. The dynamics of P. setaceum invasion and spread makes it a good model for management of similar emerging invasive perennial grasses in similar ecosystems. / AFRIKAANSE OPSOMMING: Klimaatsverandering en biologiese indringing is grootskaalse komponente van mensgedrewe globale veranderinge, en kan ook gesien word as prominente drywers van die huidige afname in globale biodiversiteit van terrestriële ekosisteme. Hierdie drywers werk saam in sinergie, en laat sodoende ekosisteme kwesbaar vir indringing deur uitheemse indringerplante. Grasse is ‘n groep indringerplante wat maklik reageer ten opsigte van globale veranderinge en verander inheemse plantgemeenskapstruktuur en ekosisteem prosesse, soos byvoorbeeld veldbrand frekwensie. Tot op hede is daar wynig studies gedoen wat die ekologiese drywers en effekte van indringergras spesies in droë en semi-droë ekosisteme van Suid-Afrika assesseer. Pronkgras (Pennisetum setaceum) is ‘n wyd verspreide meerjarige uitheemse indringergras, oorspronklik vanaf Noord-Afrika en die Midde-Ooste, en word waardeer deur tuinboukundiges wêreldwyd. Dit versprei al langs padrande aan die buitewyke van meeste dorpe, en is algemeen op ou mynhope in verskeie dele van Suid-Afrika. Somtyds ontsnap hierdie gras langs dreineringskanale of na veldbrande, en beland so in die omringende natuurlike plantegroei. Hierdie gras kan ‘n duur probleem word vir landbou asook biodiversiteit bewaring omdat dit onsmaaklik is vir diere, en dit verhoog veldbrand risiko. ‘n Beter begrip van pronkgras verspreiding en indringingdinamika sal bydra tot verbeterde bestuur en kontrole praktyke. Die hoofdoel van hierdie studie was om die ekologie en indringing prosesse van P. setaceum regoor Suid-Afrikaanse omgewingsgradiente te begryp, en dit dan te gebruik as ‘n model om die sinergistiese verhoudings tussen biologiese indringing en ander globale veranderinge (klimaat en grondgebruik) te verstaan. Die studie verskaf die eerste assessering van hoe P. setaceum verskillende indringing hindernisse in Suid-Afrika oormeester as ‘n opkomende indringer, in vergelyking met ander dele van die wêreld waar dit al klaar problematies is. Hierdie studie verskaf uiteindelik ‘n aantal bestuur en kontrole opsies vir hierdie en ander soortgelyke meerjarige grasse. Die studie verskaf spesifiek ‘n deeglike verstaan van: 1) die verspreiding en habitat voorkeure van P. setaceum in droë en semi-droë areas in Suid-Afrika, 2) omgewingshulpbronne en habitat toestande wat hierdie plant se indringing potensiaal verhoog, 3) groei- en voortplantingsvertoning oor verskillende omgewingsgradiente, 4) die reaksie wat ‘n droë ekosisteem toon teenoor P. setaceum indringing en veldbrand verhoging, en 5) die toekomstige verspreiding van hierdie gras in Suid-Afrika onder voorspellings van klimaatsverandering en verspreiding. Die studie het gevind dat pad-rivier tussengange ideale liggings is vir P. setaceum vestiging, en dat hierdie liggings dus geteiken moet word vir bestuur en kontrole doeleindes. P. setaceum toon volharding onder diverse bioom omgewings, wat toegeskryf word aan plaaslike aanpassing. Daar is gevind dat versteuring ‘n groot faktor is in die verhoging van pronkgras indringing in semi-natuurlike areas weg van padskouers. Grootskaalse pronkgras uitroeiing projekte moet fokus op versteurde gebiede, veral in die vrugbare dele van die fynbos streek, waar hierdie gras hoë klimaatsgeskiktheid toon. Bestuur en kontrole programme moet ook fokus op areas met hoë nutriente inhoud en ekstra water, aangesien hierdie areas groei en voortplanting vergemaklik. Die dinamika van P. setaceum indringing en verspreiding maak dit ‘n goeie model vir die bestuur van soortgelyke opkomende meerjarige indringergrasse in soortgelyke ekosisteme.